In the usual practice of xerography, an electrostatic latent image of an object is formed on a recording medium called a xerographic plate. The xerographic plate may comprise a very thin layer of photoconductive insulating material such as selenium on a conductive metal backing such as brass. In a recent development, the conductive metal backing portion of the xerographic plate is shaped in the form of an endless flexible band or belt. Xerographic belt substrates have been made by joining together the ends of a strip of brass such as by welding, but the seam produced where the two ends of the strip are joined is an undesirable feature in that it reduces the overall lifetime of the belt and necessitates indexing the printing cycle of the machine or system in which the xerographic belt is used so that the electrostatic latent image will not be formed on the belt where the seam is located.
A preferred method of making belts is to electroform a metal on a mandrel in an electrolytic bath. A primary problem however, has been to obtain a mandrel upon which a metal coating such as nickel could be formed, yet easily removed without damaging the mandrel. Although it has previously been suggested that materials can be easily separated from each other when they have sufficiently different coefficients of expansion, it has been found that many other factors must be considered and that a method for easily removing electroformed nickel belts from a mandrel was not available. For example, although the coefficients of thermal expansion for nickel and aluminum are sufficiently different to suggest that the nickel could be easily removed if deposited directly on the aluminum (the coefficient of thermal expansion for aluminum is 23.4 times 10.sup.-.sup.6 inches per inch per degrees C, and 13.3 times 10.sup.-.sup.6 inches per inch per degrees C for wrought nickel), it would not be practical to plate nickel directly on the aluminum mandrel because the aluminum would dissolve in the bath and secondly, nickel is not easily separated from aluminum without abrading the aluminum. Consequently, it has not been a simple matter to deposit a removable metal on a mandrel of another metal since, as noted in Hutchins U.S. Pat. No. 1,709,268, there must be a surface upon which a good birth of deposit can be made, the metal to be coated must be insoluble or practically insoluble in the electrolyte and the attachment must not be so good that it cannot later be removed. (Column 1, lines 25-43) A forth requisite not mentioned by Hutchins is that the metal to be deposited must have a sufficiently different coefficient of expansion from the mandrel. It is these problems to which this invention is directed.